Warren Cox received his BA, magna cum laude, from Yale University in 1957, following with his Master in Architecture in 1961, again at Yale. While at the Yale Architectural School, Cox edited Perspecta, the architectural review, received the Henry Adams Prize and spent two summers working for the BBPR architectural firm in Milan, Italy. After a year as Technology Editor of Architectural Forum magazine, he became a designer at Keyes, Lethbridge and Condon of Washington, DC, until 1965 when he and George Hartman founded Hartman-Cox Architects.

The firm's major areas of practice have been in the design of commercial office buildings and institutional buildings (museums, libraries, academic and government buildings), with special emphasis on demanding urban or historic contexts and with a high level of detail and finish. Over the years, the firm has undertaken increasingly large projects, working extensively in the Washington, DC, metropolitan area, with a large number of notable commissions in the monumental core/Pennsylvania Avenue corridor. In recent years, Hartman-Cox has undertaken major projects throughout the United States.

In addition to his active role as partner, Warren Cox has taught at Yale University, Catholic University, and the University of Virginia and is a Fellow of the American Institute of Architects. He has served on the Georgetown Board of the Commission of Fine Arts and the boards of the DC Preservation League and the Center for Palladian Studies in America. He has also served on a multitude of architectural design awards juries and lectured extensively throughout the country.